I have a 2006 Chrysler Town & Country. When I make a left hand turn I hear a harmonic sound. My husband thinks that the brakes are connecting with the drum even when not applied. The dealership have already already replaced the power steering pump reservoir but I still have the same sound going on.
A sticking brake caliper is not likely to produce a “harmonic sound”–assuming that I know what type of sound you are referring to. A noise that is heard when turning is more likely to be coming from the power steering system, or a bad CV joint, or perhaps a bad wheel bearing.
The next time that you hear this sound, pull over and carefully check the temperature of each wheel and wheel hub. If you find one that is hotter than the others, that could indicate a sticking brake caliper or a bad wheel bearing.
I would really suggest that you have your mechanic take a ride with you so that you can have him hear the sound to which you are referring.